Wireless computing devices, such as laptop computers, personal digital assistant devices, etc., that communicate with other devices through wireless transmissions are becoming increasingly popular. Wireless computing devices are typically battery-powered. Since the amount of power a battery can provide is rather limited, how to minimizing power consumption to extend the operation time of the device powered by the battery is an important issue for those devices.
One component in a wireless device that consumes a significant amount of power is the network interface module, which handles wireless transmission and reception of network communication data. It has been estimated that on the average about 20% of the total power consumed by a wireless laptop computer is spent on wireless LAN interface communications. Most of that energy is used for wireless data transmissions and receptions. In order to reduce the power consumption, most wireless devices employ a power-management scheme that allows the network interface module to be switched between different power states with different power consumption levels. Those states include high-power states in which the transmitter is powered up to enable the transmission and reception of network communication data, and low-power states in which the network interface module is put in a sleep mode or turned-off. The time period in which the network interface module is put in a low-power state is often referred to as the “idle time.” Since the transmitter is turned off when the network interface module is in a low-power state, the transmission of network traffic data is delayed, and the delayed traffic data have to be temporarily stored in queue, waiting to be transmitted when the network interface module is switched back to the high-power state. A significant amount of delayed network traffic data may be accumulated in the transmission queue if the interface network card is put in the low-power states too often or for too long. Thus, it is necessary to strike a reasonable balance between saving the battery power and avoiding undue network traffic congestion. Accordingly, there is a need for a new power management scheme for determining when to switch the network interface module of a wireless device into a low-power state and for how long to provide sufficient power saving without causing excessive delay and accumulation of the network traffic (i.e., traffic congestion).